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Old 03-29-2012, 10:49 AM   #41
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RE: Bottom Cleaning

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rwidman wrote:
A friend of mine was told by a mutual friend and boat owner that he was moving to another marina downriver.* His diver told him that his anodes were being disolved because of electricity in the water from a train bridge about a mile up river (this is not an electric train).

I call BS, but I didn't talk to the diver personally.

*
*

*I have found in the marine maintenance business, and the hull cleaning industry in particular, that there are a lot of people who don't know their ass from a hole in the ground. This guy sounds like he was one of them.
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Old 03-29-2012, 11:02 AM   #42
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RE: Bottom Cleaning

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My personal opinion is that a galvanic isolator is never a bad idea. However, I also think the "hot harbor" is a wive's tale. You can go to virtually any marina anywhere and find somebody who will say it's "hot" there. I have heard this in virtually every marina I have ever worked in in the Bay Area, and I have yet to find it to be true. Marina-wide problems are rare, IMHO. That being said, if you are plugged into the shorepower system, your boat is in electrical contact with every other boat on that particular circuit and you can be sharing somebody else's electrical problems. But in reality, if you are experiencing rapid zinc depletion or corrosion issues, the most likely cause is aboard your own boat and that's the place to look first.
*I wonder about that as well. However, we had our boat in a marina where we had a row of houseboats directly behind us and we experienced massive depletion of our zincs. Once we moved to a different marina the depletion dropped dramatically. We had/have shorepower in both situations.
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Old 03-29-2012, 09:21 PM   #43
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I guess we are lucky here in the PNW. At my marina, Zinc usually will last a full year and I don't hand clean the hull. I use an ablative paint and would not be fond of brushing the paint to clean the hull. Usually an hour of running is enough to clean what little has grown, off the hull. My diver checks the hull and zinc several times during the year and replaces the zinc in March or April each year.
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Old 03-29-2012, 10:03 PM   #44
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*
Just because a zinc is disolving does NOT mean it's working.

All boats SHOULD come with Galvanic Isolators or Transformers but sadly they don't/
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Old 03-29-2012, 10:48 PM   #45
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Just because a zinc is disolving does NOT mean it's working.
Then what is it doing if not working?
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Old 03-30-2012, 06:55 AM   #46
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Then what is it doing if not working?
Eroding...galvanic action...several reasons...

But if it is not enough or if there is no continuity with the metal it's attached to...then it ain't helping that metal (or helping it enough).
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Old 03-30-2012, 10:56 AM   #47
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Just because a zinc is disolving does NOT mean it's working.
Yeah, I gotta disagree with that. Yes, it's possible that there is not enough zinc to protect adequately, but zincs don't simply "dissolve". If they are depleteing, it's because they're doing their job.
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Old 03-30-2012, 04:47 PM   #48
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Yeah, I gotta disagree with that. Yes, it's possible that there is not enough zinc to protect adequately, but zincs don't simply "dissolve". If they are depleteing, it's because they're doing their job.
Think about it...underwater metal is affected by galvanic action that doesn't have zinc on it and is more nobel than zinc.

So why can't zinc underwater be subject to that same galvanic action?

If the zinc is isolated from the metal it is trying to protect by corrosion or poor connection or paint...it doesn't protect but will still go bye-bye just like your rudder and props eventually.

Without a DIRECT electrical connection between the zinc and the metal it's trying to protect...the zinc in the props, etc will still start to react in a galvanic way. Even with plenty of zincs on other underwater parts...I have seen props and prop nuts destroyed because of lack of zinc.
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Old 03-30-2012, 04:58 PM   #49
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All boats SHOULD come with Galvanic Isolators or Transformers but sadly they don't/

Yeah buy one or make one and install it.

I used two bridge rectifiers wired in sequence so the current go's in a loop wired into the green wire from shore power. mounted on a big chunk of aluminum angle as a heat sink.
About $20.00
Sd
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Old 03-30-2012, 05:02 PM   #50
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Think about it...underwater metal is affected by galvanic action that doesn't have zinc on it and is less nobel than zinc.

So why can't zinc underwater be subject to that same galvanic action?

If the zinc is isolated from the metal it is trying to protect by corrosion or poor connection or paint...it doesn't protect but will still go bye-bye just like your rudder and props eventually.

Without a DIRECT electrical connection between the zinc and the metal it's trying to protect...the zinc in the props, etc will still start to react in a galvanic way. Even with plenty of zincs on other underwater parts...I have seen props and prop nuts destroyed because of lack of zinc.
Galvanic corrosion occurs when two dissimilar metals are in contact with each other in an electrolyte. How is this happening in the scenario you describe?
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Old 03-30-2012, 05:09 PM   #51
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Galvanic corrosion occurs when two dissimilar metals are in contact with each other in an electrolyte. How is this happening in the scenario you describe?
I bolded the most pertinent words in the above statement. Plumbing 101.

If there is no direct contact between the dissimilar metals galvanic corrosion will not occur.
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Old 03-30-2012, 05:29 PM   #52
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Galvanic corrosion occurs when two dissimilar metals are in contact with each other in an electrolyte. How is this happening in the scenario you describe?

OK...I see the point....but zincs do seem to "dissolve without that majical connection" maybe it's because they are not pure zinc but an alloy?
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Old 03-30-2012, 05:33 PM   #53
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Nevermind...you didn't think it through...otherwise you don't need zincs at all.

They DON"T have to need to be connected...just immersed...
I suggest you Google "galvanic corrosion", because you clearly don't understand the definition of the term.
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Old 03-30-2012, 05:43 PM   #54
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I suggest you Google "galvanic corrosion", because you clearly don't understand the definition of the term.
Sorry long day...I wasn't thinking it through...but still feel like the whole issue of zincs doing their job is more about regular monitoring than the "wait and see appproach"...then it's too late for some.

You at least see them on a more regular basis.
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Old 03-30-2012, 05:45 PM   #55
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An anode + a cathode + seawater = a battery.
electrons migrate.
Two disimilar metals in seawater.
One becomes the anode the other becomes the cathode.
electrons migrate ( or disolve) from the least noble metal.
Zinc is the least noble metal on your boat.
It disolves.
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Old 03-30-2012, 10:45 PM   #56
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Sorry long day...I wasn't thinking it through...but still feel like the whole issue of zincs doing their job is more about regular monitoring than the "wait and see appproach"...then it's too late for some.

You at least see them on a more regular basis.
Don't ever doubt me again.
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Old 03-31-2012, 01:32 AM   #57
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Call me stupid believing a dissolving zinc isn't doing its job.
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Old 03-31-2012, 09:21 AM   #58
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Then what is it doing if not working?
It's ballast.
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